The present invention relates to a cyanoacrylate adhesive composition superior particularly in heat resistance and hot-cold cycle resistance.
An .alpha.-cyanoacrylate adhesive polymerizes and cures rapidly in the presence of trace water absorbed on the surface of a material to be bonded, affording an extremely strong bond in a short time for almost all materials except some inert materials such as polyethylene and Teflon. Because of such a superior property .alpha.-cyanoacrylate adhesives are widely in use as instantaneous adhesives of a room temperature setting one-part type for the bonding of metals, plastics, rubber, wood, etc.
However, since cyanoacrylate polymer is a brittle polymer, cyanoacrylate adhesives have the drawback that they are inferior in peeling bond strength and impact resistance. With a view to remedying such a drawback there have been proposed cyanoacrylate adhesive compositions modified with various elastomers, core-shell polymers, adhesives and reinforcing agents.
JP43-29477B discloses a cyanoacrylate adhesive composition containing one or more elastomers selected from (1) the reaction product of polyester and/or polyether and polyisocyanate, (2) acrylonitrile-butadiene rubber having carboxyl group and (3) acrylic ester based polymer.
JP53-30643A discloses a cyanoacrylate adhesive composition improved in peeling strength and containing an elastomer selected from (1) acrylonitrile-butadiene-styrene terpolymer, (2) methacrylate-butadiene-styrene terpolymer and (3) acrylonitrile vinylidene chloride copolymer whose vinylidene chloride content is at least 50 mol %.
JP63-284279A discloses a cyanoacrylate adhesive composition containing a saturated copolyester and improved in peeling bond strength and impact strength.
JP4-75268B discloses a cyanoacrylate adhesive composition containing a copolymer of acrylic ester of methacrylic ester and a lower alkene monomer.
JP5-1831B discloses a cyanoacrylate adhesive composition comprising urethane rubber and pyrogallol and improved in all of tensile shear bond strength, peeling bond is strength, impact peeling bond strength, and resistance to heat, water and moisture.
U.S. Pat. No. 4,102,945 discloses a cyanoacrylate adhesive composition containing a core-shell copolymer selected from acrylonitrile-butadiene-styrene terpolymer (ABS), methacrylate-butadiene-styrene terpolymer (MBS) and vinylidene chloride-acrylonitrile copolymer (VAC), as an impact resistance improver for polyvinyl chloride resin.
U.S. Pat. No. 4,560,723 (JP5-59949B) discloses a cyanoacrylate adhesive composition comprising a core-shell copolymer as a reinforcing agent which has been freed from impurities causing premature polymerization of a cyanoacrylate adhesive and an agent for the prevention of heat aging.
For adhesives used to bond mechanical parts and the like which are used in outer environments it has been considered necessary to have not only a high bond strength in normal state but also a high adhesive force even against changes in atmospheric temperature caused by the difference in temperature between daytime and night, change of season, etc. But conventional cyanoacrylate adhesive compositions do not fully satisfy these characteristics required.
Accordingly, it is the object of the present invention to provide a cyanoacrylate adhesive composition which satisfies the above characteristics required.
Having made studies earnestly to achieve the above-mentioned object, the present inventors found out that a cyanoacrylate adhesive composition containing an elastomer and a core-shell polymer not only possesses high shear adhesive force, peeling bond strength and impact adhesive force but also exhibits an outstanding effect of improvement particularly in hot-cold cycle resistance and heat resistance.